I am trying to replace my old mercury thermostat wired Y, G, W, R, with a new thermostat has an Rh, Rc..?

Hi I am trying to replace my old mercury thermostat (had four wires connected to it, Y, G, W, R) with a new Honeywell RTH 111 non programable simple thermostat that has an Rh Rc, Y, G, W. (There is a blue wire but that was never connected to anything). I am wondering which port do I put the Red wire into?